Stock-based Compensation (Tables)

3 Months Ended

Apr. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Classification of Stock-based Compensation

The following table presents the classification of stock-based compensation for the periods indicated:

	Three Months Ended April 30,
	2018		2017
	(in thousands)
Stock-based compensation:
Cost of revenue	$	315	$	303
Research and development		8,760		7,977
Selling, general and administrative		5,120		4,692
Total stock-based compensation	$	14,195	$	12,972

Weighted-Average Assumptions Used to Estimate Fair Value

The following table sets forth the weighted-average assumptions used to estimate the fair value of stock options and employee stock purchase plan awards for the periods indicated:

	Three Months Ended April 30,
	2018			2017
Stock Options:
Volatility		55	%		53	%
Risk-free interest rate		2.65	%		2.17	%
Expected term (years)	5.33			6.07
Dividend yield		0	%		0	%
Employee stock purchase plan awards:
Volatility		46	%		39	%
Risk-free interest rate		1.95	%		0.89	%
Expected term (years)		0.5			0.5
Dividend yield		0	%		0	%

Stock Option Activities

The following table summarizes stock option activities for the period indicated:

	Option Outstanding
										Weighted-
								Total Intrinsic		Average
						Weighted-		Value Of		Remaining		Aggregate
				Weighted-		Average		Options		Contractual		Intrinsic
				Average		Grant-date		Exercised		Term		Value
	Shares			Exercise Price		Fair Value		(in thousands)		(in years)		(in thousands)
Outstanding at January 31, 2018		1,611,344		$	24.56
Granted		21,900			49.91	$	25.48
Exercised		(42,483	)		7.17			$	1,853
Forfeited		(8,921	)		55.40
Expired		(561	)		71.16
Outstanding at April 30, 2018		1,581,279			25.19					4.51		$	39,119
Exercisable at April 30, 2018		1,354,895		$	20.32						3.85	$	38,705

Restricted Stock and Restricted Stock Units Activities

The following table summarizes restricted stock and restricted stock units activities for the period indicated:

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2018		2,103,281		$	56.45
Granted		28,620			49.91
Vested		(248,658	)		53.36
Forfeited		(13,097	)		54.02
Unvested at April 30, 2018		1,870,146		$	56.78